agridat (version 1.23)

byers.apple: Diameters of apples

Description

Measurements of the diameters of apples

Format

A data frame with 480 observations on the following 6 variables.

tree

tree, 10 levels

apple

apple, 24 levels

size

size of apple

appleid

unique id number for each apple

time

time period, 1-6 = (week/2)

diameter

diameter, inches

Details

Experiment conducted at the Winchester Agricultural Experiment Station of Virginia Polytechnic Institute and State University. Twentyfive apples were chosen from each of ten apple trees.

Of these, there were 80 apples in the largest size class, 2.75 inches in diameter or greater.

The diameters of the apples were recorded every two weeks over a 12-week period.

Examples

if (FALSE) {
  
  library(agridat)
  data(byers.apple)
  dat <- byers.apple

  libs(lattice)
  xyplot(diameter ~ time | factor(appleid), data=dat, type=c('p','l'),
         strip=strip.custom(par.strip.text=list(cex=.7)),
         main="byers.apple")

  # Overall fixed linear trend, plus random intercept/slope deviations
  # for each apple.  Observations within each apple are correlated.
  libs(nlme)
  libs(lucid)
  m1 <- lme(diameter ~ 1 + time, data=dat,
            random = ~ time|appleid, method='ML',
            cor = corAR1(0, form=~ time|appleid),
            na.action=na.omit)
  vc(m1)
  ##       effect   variance   stddev corr
  ##  (Intercept) 0.007354   0.08575    NA
  ##         time 0.00003632 0.006027 0.83
  ##     Residual 0.0004555  0.02134    NA
}